by When it comes to detecting the presence of liquid water on planets outside the solar system, and thus the conditions necessary for life, the James Webb Space Telescope (JWST) may want to look at what’s missing rather than what’s there. This is what that means.
A team of researchers, including scientists from the Massachusetts Institute of Technology (MIT) and the University of Birmingham, suggests that rocky worlds such as Earth outside the solar system have less carbon dioxide in their atmospheres than other planets. in the same system. , this could be a sign that they heard liquid water. And as we know from the formation of life on our own planet, and the conditions necessary to support life here, the presence of liquid water is a key indicator of possible habitability.
Although the search for key chemical components that indicate habitability on extrasolar planets, or exoplanets, is just within the reach of current technologies, depleted carbon dioxide is a sign that the JWST is now ready to observe.
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“The Holy Grail of exoplanet science is the search for habitable life and the presence of life, but all the aspects discussed so far are beyond the newest observatories,” Julien de Wit, member discovery team and an assistant professor of planetary sciences at MIT, said in a statement. “We now have a way to find out if there is liquid water on other planets. And it’s something we can achieve in the next few years.”
A roadmap to discovering life on exoplanets
Currently, scientists are very good at using tools to determine how far a planet is from its host star and therefore whether it is in that star’s “habitable zone” – defined as the region that is not too too hot or too cold to be allowed to exist. liquid water.
In our own solar system, however, Earth, Mars and even Venus are all in the habitable zone around the sun. However, only one of those planets is capable of supporting life as we know it. That means habitability is not the same as preserving liquid water for exoplanets and location, location, location. So, currently, scientists do not have a solid way to confirm whether a planet is habitable or not.
Considering the Earth, Mars and Venus as well as the differences between the three, the team realized that the only one with habitability, Earth, also has a depleted atmosphere of carbon dioxide compared to its habitable zone neighbors.
“We assume that these planets were created in the same way, and if we see one planet with much less carbon now, it must have gone somewhere,” Triaud said. “The only process that could remove so much carbon from the atmosphere is a strong water cycle involving liquid water oceans.”
Over billions of years, our planet’s oceans have been responsible for removing huge amounts of carbon dioxide from the atmosphere, meaning it now has less than Venus or Mars.
“On Earth, much of the atmospheric carbon dioxide has been sequestered in seawater and solid rock over geological time scales, which has helped regulate climate and habitability for billions of years,” Frieder Klein, co-author of the research and scientist at the Woods Hole Oceanographic Institute (WHOI), said in the statement.
That led the team to think that the depletion of carbon dioxide in an exoplanet’s atmosphere could also indicate the presence of liquid oceans.
A search with these parameters would be more suitable for “pea-in-a-pod” planetary systems that, like the solar system, host multiple rocky or terrestrial worlds of similar sizes orbiting their star at similar distances.
The first step in the investigation suggested by the team is to look for carbon dioxide and use this as an indicator that the exoplanet targets have an atmosphere. Once it is determined that multiple planets in one system have atmospheres, the next step is to find out how much carbon dioxide is in the atmospheres.
This should indicate whether one or more of the planets has significantly less carbon dioxide than the others, indicating that it likely has oceans of liquid water and may be habitable so.
Of course, there is a bit more to this method than just comparing carbon dioxide abundances. “Novelty” is not the same as “inhabited.” To check if life could really exist on an exoplanet indicated by the absence of carbon dioxide, the team recommends looking for another molecule: Ozone.
Composed of three oxygen atoms, ozone is a molecule created when life forms such as plants and microorganisms release carbon dioxide from the Earth’s atmosphere then oxygen molecules hit by sunlight. Ozone is a good measure of these processes on alien life because it is easier to detect distant exoplanets in the atmosphere than oxygen itself.
The team says that if a planet’s atmosphere shows signs of carbon dioxide depletion along with an abundance of ozone, it could well be habitable – and inhabited by humans.
“If we see ozone, there is a pretty high chance that it is connected to carbon dioxide being consumed by life,” said Triaud. “And if it’s life, it’s glorious life. It would be just a few bacteria. It would be a planetary-scale biomass capable of processing and interacting with an enormous amount of carbon.”
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The researchers believe that the JWST is already able to measure the abundance of carbon dioxide and ozone in near-Earth multiplanet systems.
This includes the TRAPPIST-1 system, located 40 light-years away, which is known to host seven earth-like planets, several of which are in the habitable zone of its cool star.
“TRAPPIST-1 is one of a handful of systems where we could do terrestrial atmospheric studies with JWST,” de Wit concluded. “We now have a roadmap for finding habitable planets. If we all work together, paradigm-shifting discoveries could be made in the next few years.”
The team’s research was published on December 28 in the journal Nature Astronomy.
